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we 1,865,355; rI F 1 ir/ July 5, 1932. A. HUND 1,865,858

PIEZO ELECTRIC CRYSTAL SYSTEM Fild April 29, 1929 ELECTRICAL AXISOPTICAL AXIS ELECTRICAL T AXIS OF T/ CA L m AXIS I i .gw sanznse 1 !UNPatented July 5, 1932 UNITED STATES udIT-Ii msiii'l PATENT OFFICE AUGUSTHUND, OF BETHESDA, MARYLAND PIEZO ELECTRIC CRYSTAL SYSTEM Applicationfiled April 29, 1929. Serial No. 359,113.

My invention relates broadly to high frequency oscillators and moreparticularly to a piezo electric crystal controlled oscillator system.

One of the objects of my invention is to provide a piezo electriccrystal oscillator system in which the capacity effects of theelectrodes associated with the piezo electric element of crystallinequagtz may be reduced to a minimum for obtaining constant frequencyoscillations in an electrical system controlled accurately by thefrequency characteristics of the piezo electric crystal element.

Another object of my invention is to provide a system for producingoscillations in an electrical system under control of a piezo electriccrystal element in which a composite oscillation along a multiplicity ofaxes of the piezo crystal is developed in the piezo electric crystal forproducing constant frequency control in an associated electricalcircuit.

Other and further objects of my invention reside in the construction andarrangement of mounting for piezo electric crystals for obtainingoscillations as set forth more clearly in the specification hereinafterfollowing by reference to the accompanying drawing, in which:

Figure 1 diagrammatically illustrates a piezo electric. crystal systemembodying the principles of my invention; and Fig. 2 is a side elevationof a piezo electric crystal arranged in accordance with my inventionwhere the crystal is shown partially in side elevation and partiallybroken away and illustrated in section.

I have discovered that a high degree of constancy in the frequencycharacteristic of energy generated by a piezo electric crystal systemmay be secured when the capacity effects of the electrodes by which thepiezo electric crystal element is connected in the oscillator system arereduced to a minimum.

- I have further discovered that by setting up oscillations in a piezoelectric crystal system which have components along several axes in thecrystal system, that a frequency characteristic of a high degree ofconstancy may be obtained. In the piezo electric crystal system of myinvention, I establish connec tion with the opposite sides of theoscillatory circuit to which the piezo electric crystal element isconnected by a connection between one face of the crystal and aconnection to the sides of the crystal. The piezo electric effect takesplace between the connection on the exterior cylindrical surface of thepiezo electric crystal element and one face of the piezo electriccrystal element, thus reducing the capacity of the crystal mounting to aminimum.

Referring to the drawing in more detail, the piezo electric crystalelement is indicated by reference character 1 having one face thereofresting in contact with contact plate 2 which connects to one side ofthe high frequency oscillator system which may include electron tube 3containing cathode 3a, control member 3b and plate electrode 30.Suitable means may be provided for controlling the potential of thecontrol member 3?) such as potential source 4: operating through highresistance path 5. The output of the oscillatory circuit may includetuned circuit 6 and source of potential 7 the oscil- .lations beingtransferred to the coupled circuit- 8. Connection is made between thecontrol electrode 3?) of the piezo electric crystal element and thepiezo electric crystal element 1 by means of a band member 9 which maybe of copper or other metallic material which loosely encircles theexterior surface of the sides of the crystal element 1. The hand 9 ismade of small dimensions to reduce the capacity effects betweenelectrodes to a minimum. The energy which is transferred to the electrontube oscillator circuit takes the path indicated by dotted lines 10. Theelectrostatic lines therefore proceed along different components, one ofwhich is parallel to the axis of the cylinder and the other of which issubstantially at right angles to the optical axis of the crystal andalong one of the piezo electric axes. I have found that the electricoscillations thus developed have the characteristic of extreme constancyin frequency and thereby enable an electron tube oscillator system to becontrolled according to the crystal freqifency and independent ofcircuit characteristics and free of capacity effects which normally tendto introduce inaccuracies in the frequency of the oscillations developedby the crystal control system.

The position of the ring-member 9 which encircles the perimeter orperiphery of the piezo electric crystal element 1 with respect to theplate member 2, is selected to provide such spacial relationship as maybe required in securing operation of the oscillatory systern at apredetermined selected frequency. The ring member 9 may be adjusted inposition along the surface of the sides of the piezo electric crystalelement 1 until that position is reached at which oscillations of thedesired frequency are sustained in the oscillatory system.

\Vhile I have described the piezo electric crystal system of myinvention, in one of its preferred embodiments, I desire that it beunderstood that modifications may be made and that no limitations uponmy invention are intended other than are imposed by the scope of theappended claims.

lVhat I claim as new and desire to secure by Letters Patent of theUnited States is as follows:

1. Means for establishing electrical connection with a piezo electriccrystal element having the electrical axis coincident with thegeometrical axis thereof with the optical axis extending normal theretocomprising a plate contacting with one face of said piezo electriccrystal element and a member encircling the periphery of said piezoelectric crystal element in a plane parallel to the optical axis of saidcrystal element.

2. Means establishing connection with a piezo electric crystal elementhaving the electrical axis thereof coincident with the geometrical axiswith the optical axis extending normal thereto comprising a pair ofelectrodes, one of said electrodes establishing connection with one faceof said piezo electric crystal element, and the other of said electrodesestablishing connection with the periphery of said piezo electriccrystal element in a plane parallel to the optical axis of said piezoelectric crystal element.

3. Means for establishing electrical connection with a piezo electriccrystal element having the electrical axis thereof coincident with thegeometrical axis and having the optical axis extending normal theretocomprising a plate electrode connected with one face of said crystalelement and a ring member encircling the periphery of said crystalelement and positioned in the path of piezo electric effects extendingsubstantially parallel to the optical axis of said piezo electriccrystal element and substantially at an angle thereto.

4. Means for establishing electrical connection with a piezo electriccrystal element having the electrical axis thereof coincident with thegeometrical axis with the optical axis extending normal theretoincluding a plate member contacting with one face of said piezo electriccrystal element, and a conductive band of small electrical capacityengaging the periphery of said piezo electric crystal element in a planeparallel to the optical axis of said piezo electric crystal element.

5. A mounting for a cylindrical shaped piezo electric crystal elementhaving an axially extending electrical axis and a radially extendingoptical axis, including connections for said piezo electric crystalelement comprising a plate member contacting with one face of said piezoelectric crystal element, and a loose fitting ring-like memberencircling the cylindrical surface of said piezo electric crystalelement in a plane parallel to the optical axis of said piezo electriccrystal element.

6. A mounting for a piezo electric crystal element having the electricalaxis thereof coincident with the geometrical axis and the optical axisextending at right angles thereto, including electrodes constituting aplate member contacting with one face of said piezo electric crystalelement, a conductive ringlike member encircling the periphery of saidpiezo electric crystal element in a position removed from theaforementioned face of said piezo electric crystal element in a planesubstantially parallel to the optical axis of said piezo electriccrystal element, and terminal connections extending from said platemember and said ring-like member.

7. A mounting for a piezo electric crystal element having the electricalaxis thereof extending normal to the faces of the crystal and theoptical axis electrically parallel to the faces of the crystalcomprising a plate member establishing a connection with one face ofsaid piezo electric crystal element, a member encircling the peripheryof said piezo electric crystal element and said member being positionedremote from the faces of said piezo electric crystal element in a planesubstantially parallel with the optical axis of said piezo electriccrystal for establishing paths for the passage of piezo electriccurrents through said piezo electric crystal element along separatecomponents of the axes of said element.

8. A piezo electric crystal assembly comprising a circular piezoelectric crystal element having a cylindrical surface with theelectrical axis extending axially and its optical axis extendingdiametrically, a conductive plate adapted to establish electricalconnection with one end of the circular piezo electric crystal elementand a conductive belt of small electrical capacity extending around thecylindrical surface of said piezo electric crystal element andestablishing electrical connection therewith in a plane parallel withthe optical axis of said element.

9. A piezo electric crystal assembly comprising a circular piezoelectric crystalelement having a cylindrical surface with the electricalaxis extending axially and its optical axis extending diametrically, aconductive plate adapted to establish electrical connection with oneface of the circular piezp electric crystal element and a conductivebelt extending around the cylindrical surface of said piezo electriccrystal element and establishing electrical connection therewith in aplane parallel with the optical axis of said element, said belt havin awidth substantially less than one-half t e thickness of said piezoelectric crystal element.

In testimony whereof I aifix my signature.

AUGUST HUND.

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